So it's been quite a while since I've posted, (the truck has been a dream for several months) and I had a coolant leak at the thermostat outlet. Changed the fitting and thermostat and sealed with lots of blue monkey snot. It's been perfect for a couple months but a week ago it started leaking again. Exactly the same as last time. I'm wondering if anybody has any tips or tricks or something I may have missed. I cleaned the mating surface of the water pump with a plastic scraper to remove the old sealer and then finished it with fine scotch brite. I looked at several parts breakdowns and none of them showed a gasket.......

 

You have two types of Thermostats to choose from. The Older one uses a gasket between the T-Stat and the Flange. The newer (Superseded Previous P/N) has a Gasket which surrounds the T-Stat and seals both the Pump and Housing when torqued; 15 ft. lb.

The Housing is for all practical purposes "single use" IMO. I have cleaned them up and reinstalled with a thin RTV bead. And, not had a comeback.

 

But any idea what I did wrong the first time? It's got the later style seal. I had to replace the water pump last September and it was all the new style. Would you typically use rtv on the initial install?

 

Yes, on the RTV. Real thin layer of black.

 

I figured so. I put it together with the blue water pump and thermostat stuff. I'll go back together with black when I go through it this weekend. AGAIN

 

I seem to recall an oring seal at the tstat housing, then bi chased it with black rtv

 

I'd replace the outlet if you're having leaks, they are kinda flimsy. Not too expensive. Or bling it up with a billet one that will last.

 

That housing is only a month old so they better warranty it. The only seal this one had is a square seal under/above the thermostat (I can't remember if it's over or under) but it sure seems like there should be one for the flange. No dice though.

 

Just fyi.... over torque will also increase a risk of leaks.

 

Honestly, if I had to guess, I would say that's the issue. It'll get a torque wrench this time

 

The Right Stuff & I think the Motorcraft RTV/gasket maker is a higher durometer when cured,always preferred these when leaks were a challenge.

 

Well I plan on pullinnit apart and goin on with a new housing Friday after work.

 

Pulled it apart 4 times the other night, to no avail. tried sealer, no sealer, new housing, new thermostat o-ring, still leaked. so now it's wearing a healthy bead of aircraft grade fuel tank sealer! no leaks yet, knock on wood.

 

This is what I used after a gentle scrub with some emery cloth.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

No leaks, no issues and going strong...

 

Another vote for Peratex "The Right Stuff". Have never had a leak after using this stuff. Pricey but worth it instead of the hassle. Hope the leak is stopped for ya.